KR100769028B1 - Inspection method and apparatus of laser crystallized silicon - Google Patents

Abstract

The present invention relates to a method and apparatus for inspecting laser crystallized silicon in a low temperature poly Si (LTPS) process. Crystal quality is examined by using a visible light source to irradiate the surface of the poly Si and inspecting changes in reflected light caused by the shape of protrusions on the surface of the poly Si. This method can be used for the poly Si samples prepared by line scanning of excimer laser annealing (ELA) technology.

Excimer laser annealing, line frequency, low temperature poly, laser, visible light source

Description

Inspection method and apparatus of laser crystallized silicon

1A-1C are atomic force microscope pictures of samples of laser crystallized silicon of a glass substrate.

2A-2C are corresponding electron micrographs of samples of laser crystallized silicon as shown in FIGS. 1A-1C.

3 shows the relationship between the amount of laser energy and the standard intensity of reflected light according to the invention;

4 shows a photograph taken by the camera according to the invention for silicon regions crystallized on a glass substrate formed in different amounts of laser energy after being irradiated with white light.

5 is a schematic diagram of equipment configuration of a method for inspecting laser crystallized silicon according to the present invention;

Explanation of symbols on the main parts of the drawings

1: platform

2: substrate

3: visible light source

4: camera

TECHNICAL FIELD The present invention relates to a method and apparatus for inspecting laser crystallized silicon, and more particularly, to a test method and a method for simultaneously monitoring the formation of laser crystallized silicon in a low-temperature poly Si (LTPS) process. It relates to an inspection apparatus.

Due to the advances in the technology of manufacturing thin film transistors, due to the advantages of smaller, much lighter, lower power consumption and no electromagnetic waves, liquid crystal displays (LCDs) are used in calculators, personal It is widely applied to various electronic products such as PDAs, wrist watches, laptops, digital cameras, mobile phones and the like. In addition, TFT-LCD devices are becoming more and more popular by lowering manufacturing costs as manufacturers aggressively invest in research and development and use large-scale manufacturing facilities.

As low temperature poly Si (LTPS) thin film transistor LCDs are superior in terms of resolution, brightness, size and anti-electromagnetic interference, LCD manufacturers are increasingly focusing on this field of technology. Given mass production requirements and the quality of the films, excimer laser annealing (ELA) is used in the LTPS process. The excimer laser is used as a heat source, and the laser light through the projection system generates energy beams with a uniform energy distribution projected onto the Si-structure on the substrate. After the a-Si structure on the substrate absorbs the energy of the excimer laser, the a-Si structure is converted into a poly Si structure. The entire annealing process is carried out below 600 ° C., and typical glass or plastic substrates can be used.

In the application of LTPS as described above, the a-Si structure deposited on the substrate is irradiated and scanned by a laser beam to form laser crystallized silicon. The quality of laser crystallized silicon directly affects the properties of the various devices formed later. However, current methods of examining the quality of crystallized silicon on a substrate are not ideal. One method is a scanning electron microscope (SEM) that examines the size, shape and distribution of grains. Since the SEM method requires cutting the substrate and chemical pre-treatment for sample analysis, this method can only be used for sampling inspection due to the fact that it cannot be used directly on the manufacturing line and destroys the substrate. Another method is a deep UV microscope that examines the shape of protrusions on the surface of crystallized silicon. However, this ultra UV microscopy method can only be used to inspect crystals of several microns on a substrate because the sample only needs to magnify the sample larger than 10,000 times and it takes several days to inspect the entire substrate. It is difficult to handle and expensive.

Therefore, in order to provide satisfactory inspection results of laser crystallized silicon, it is urgently needed to improve current inspection methods of laser crystallized silicon in the LTPS process.

It is an object of the present invention to provide a method for inspecting laser crystallized silicon applied to low temperature poly Si (LTPS) processes. The phenomenon of similar beam splitting-gratings caused by the shape of protrusions on the surface of the crystallized silicon formed on the insulating substrate through line scanning of excimer laser annealing (ELA) technology. By virtue of this, a simple and immediate method of checking the crystal quality of the surface of the crystallized silicon is provided.

It is yet another object of the present invention to provide an inspection method for simultaneously monitoring the formation of laser crystallized silicon in a low temperature poly Si (LTPS) process. A visible light source that irradiates the surface of the crystallized silicon and a camera that captures the reflected light of the light source are used in conjunction with an excimer laser annealing (ELA) machine of line scanning to monitor abnormal crystals on the surface of the crystallized silicon If found, the laser energy of the excimer laser annealing (ELA) machine is immediately corrected and adjusted.

Yet another object of the present invention is to provide an inspection apparatus using the inspection method described above.

According to a first aspect of the present invention, a laser crystallized silicon inspection method applied in a low temperature poly Si (LPTS) process uses a visible light source such as white or green light to irradiate a surface of crystallized silicon on an insulating substrate. And examining the crystal quality by changes in reflected light due to the shape of the protrusions on the surface of the crystallized silicon formed through line scanning of excimer laser annealing (ELA) technology. For example, if the changes in reflected light are large and apparent, stripes are distributed over the surface of the crystallized silicon, indicating that the crystal quality is inferior.

According to a second aspect of the present invention, an inspection method is disclosed for simultaneously monitoring the formation of laser crystallized silicon in a low temperature poly Si (LTPS) process. The method comprises performing an excimer laser annealing (ELA) technique by line scanning to transform amorphous silicon on a substrate into crystallized silicon, simultaneously using a visible light source to irradiate the surface of the crystallized silicon, Examining the crystal quality of the crystallized silicon by changes in reflected light due to the shape of the protrusions on the surface of the crystallized silicon and the laser energy of the laser beam used in the ELA technique matches the crystal conditions of amorphous silicon. Or monitoring whether the laser energy of the laser beam is unstable. For example, when the changes in reflected light are large and apparent, stripes are distributed over the surface of the crystallized silicon, indicating that the crystal quality is inferior, resulting in inadequate or unstable laser energy.

The above described aspects and advantages of the present invention will be more readily understood through the following detailed description with reference to the accompanying drawings.

A new method of inspection of laser crystallized silicon is provided herein. In the process of irradiating amorphous silicon on an insulating substrate such as a glass substrate with a laser beam through excimer laser annealing (ELA) technology of line scanning, a visible light source such as white light is used to irradiate the surface of the crystallized silicon, The quality is checked by reflected light changes due to the shape of the protrusions on the surface of the crystallized silicon. For example, when the intensity of the reflected light is large and apparent, stripes are distributed over the surface of the crystallized silicon, indicating that the crystal quality is inferior. In addition, it can also be monitored whether the laser energy of the laser beam used in ELA technology meets the crystal conditions of amorphous silicon or whether the laser energy of this laser beam is unstable.

Referring to the atomic micrographs of the crystallized silicon and the corresponding electron micrographs, respectively, FIGS. 1A-1C and 2A-2C, samples of the electron microscope are chemically processed to expose the grain boundaries of the crystallized silicon to determine the crystal. Inspect the quality.

1A and 2A show the crystal state of insufficient laser energy. It is found that the protrusions at the surface of the crystallized silicon of FIG. 1A are of random shape and the grain boundaries of the crystallized silicon of FIG. 2A are disordered. When the laser energy is increased to be optimally related to the crystalline conditions of amorphous silicon such as the thickness of the amorphous silicon film, the thickness of the silicon oxide formed on the surface of the film, and the atmosphere of the laser crystal, the crystal state of uniform and regular shape is shown in FIG. It is formed as shown in 1b and 2b. However, when the laser energy is exceeded, the regularity of the crystal state disappears as shown in Figs. 1C and 2C.

Long-term studies and observations have shown that when laser energy is optimally related to the crystallization conditions, the protrusions formed on the surface of the crystallized silicon become a uniform and regular shape, the direction of the shape being perpendicular to the scanning direction of the laser. And the spacing between the two lines of protrusions is about 2500 to 3300 nm, and the average angular distribution of the protrusions with respect to the film plane is an angle of 70 to 80 degrees. Due to the uniform and regular shape of the protrusions formed on the surface of the crystallized silicon, the surface of the crystallized silicon has a function similar to beam splitting-grafting. When a white light source is used to irradiate the surface of the crystallized silicon at an angle of about 10 to 85 degrees, preferably 15 to 30 degrees of the substrate plane, the optical path difference of the reflected lights by regularly arranged protrusions is given by Therefore, it is calculated to be 5394 to 5684 nm, which is exactly the wavelength of green light. That is, the shape of the uniform and regular protrusions can cause maximum constructive interference of bright green light. Therefore, when the observer sees within the irradiation angle range of the white light source, the observer will know that the surface of the crystallized silicon in the optimized crystal appears green.

3 shows the relationship between the intensity of reflected green light and the amount of laser energy. When the laser energy is appropriate as shown in region F of Fig. 3, the change in intensity of the reflected green light (value of ΔY / ΔX) becomes small due to the discontinuous output of the ELA laser light itself. However, when the laser energy is inadequate as shown in the E region of the insufficient laser energy and the G region of the excess laser energy in Fig. 3, the intensity change of the reflected green light for the same laser energy in the F region becomes large. Under such circumstances, the intensity variations of the green light reflected from the surface of the crystallized silicon at various locations on the substrate become evident such that the stripes are completely distributed over the surface of the crystallized silicon. In other words, when the surface of the crystallized silicon is irradiated by the white light source at an angle of about 10 to 85 degrees with respect to the plane of the substrate, an observer within the irradiation angle range of the white light source sees stripes that appear on the surface of the crystallized silicon. It can be concluded that the laser energy is inadequate. In addition, the optimal planar direction for observing whether stripes appear on the surface of crystallized silicon is perpendicular or parallel to the scanning direction of the laser.

Due to advances in modern imaging technology, cameras, such as CCD lenses with tens of millimeters of resolution, are used to replace the observer's eye capturing images of reflected light. 4 shows a photograph taken by the camera for silicon regions crystallized on a glass substrate formed by various laser energy quantities after being irradiated with white light, the laser energy being insufficient in the E region, and the laser energy being F _1. , F ₂ , and F ₃ regions become suitable, and the laser energy becomes excessive in the G region. As shown in Figure 4, the stripes are completely distributed on the surface of the crystallized silicon in the E region of insufficient laser energy and the G region of excess laser energy.

Therefore, a simple and high speed inspection method of laser crystallized silicon is designed in accordance with the above research and discovery. As shown in FIG. 5, the visible light source 3 is used to irradiate the surface of the crystallized silicon of the silicon 2 disposed on the platform 1 at an angle of about 10 to 85 degrees with respect to the plane of the substrate, and the camera (4) is used to capture the reflected images of the surface of the crystallized silicon of the entire substrate within the irradiation angle range of the light source 3. The captured images are then input into a computer for processing and analysis. For example, by analyzing the uniformity, contrast or gray scale of the light intensity of the image in the selected area, the crystal state of the selected area can be obtained to facilitate process monitoring.

The equipment necessary to carry out the method of inspecting laser crystallized silicon in the present invention is only a visible light source and a camera, and is combined with an excimer laser annealing (ELA) machine to prevent the formation of laser crystallized silicon in a low temperature poly Si (LTPS) process. The inspection device is designed to monitor simultaneously so that whenever the abnormal crystal is monitored, the laser energy of the excimer laser annealing (ELA) machine is immediately corrected and adjusted. In the method of inspecting laser crystallized silicon in the present invention, it takes only about 5 to 10 seconds to capture images reflected from the surface of the crystallized silicon on the entire about 1 m ² substrate and analyze them with computer software. In addition, the method of inspecting laser crystallized silicon in the present invention can not only inspect a situation in which laser energy becomes inadequate for the crystal conditions of amorphous silicon, but also inspect uneven crystals generated from unstable laser energy, that is, laser energy. Is set correctly, but you can check for unstable output.

Therefore, compared to conventional SEM methods and ultra UV methods, this method provided in the present invention is much faster, simpler and more economical, and is suitable for process monitoring.

  As those skilled in the art will understand, the above embodiments of the present invention are not intended to limit the present invention but to illustrate the present invention. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, which are to be accorded the broadest interpretation so as to encompass all such modifications and similar structures.

The present invention is directed to the phenomenon of similar beam splitting-gratings caused by the shape of protrusions on the surface of crystallized silicon formed on an insulating substrate through line scanning of excimer laser annealing (ELA) technology. By providing a simple and immediate method for inspecting the crystal quality of the surface of crystallized silicon, the present invention also provides a visible light source for irradiating the surface of the crystallized silicon and a camera for capturing the reflected light of the light source. Used in conjunction with the scanning excimer laser annealing (ELA) machine, it monitors crystals on the surface of the crystallized silicon to immediately correct and adjust the laser energy of the excimer laser annealing (ELA) machine whenever abnormal crystals are found.

Claims (20)

A method for inspecting laser crystallized silicon applied to a low-temperature poly Si (LTPS) process, Using a white light source to irradiate a surface of the crystallized silicon in which amorphous silicon on an insulating substrate is deformed through line scanning of excimer laser annealing (ELA) technology, the white light source being in the plane of the substrate. Using the white light source to irradiate the surface of the crystallized silicon at an angle of about 10 to 85 degrees relative to the; And Reflected images of the surface of the crystallized silicon on the same side as the light source after being irradiated by the light source to inspect the quality of crystallization by changes in light reflected by the arrangement of protrusions on the surface of the crystallized silicon And capturing the laser crystallized silicon. The method of claim 1, And when the changes in the reflected light are large and distinct, stripes are distributed over the surface of the crystallized silicon, which indicates an inferior quality of crystallization. The method of claim 1, And the white light source irradiates the surface of the crystallized silicon at an angle of about 15 to 30 degrees with respect to the plane of the substrate. delete The method of claim 1, And the white light source comprises green light. An inspection method for simultaneously monitoring the formation of laser crystallized silicon in a low temperature poly Si (LTPS) process, Performing an excimer laser annealing (ELA) technique by line scanning to deform amorphous silicon on an insulating substrate into the crystallized silicon, Simultaneously using a white light source to irradiate the surface of the crystallized silicon, wherein the white light source simultaneously irradiates the white light source to irradiate the surface of the crystallized silicon at an angle of about 10 to 85 degrees with respect to the plane of the substrate. Steps to use, Of the surface of the crystallized silicon on the same side as the light source after being irradiated by the light source to examine the crystallization quality of the crystallized silicon by changes in light reflected by the arrangement of protrusions at the surface of the crystallized silicon Capturing the reflected images, and Simultaneously monitoring the formation of laser crystallized silicon, including monitoring whether the laser energy of the laser beam used in the ELA technique does not match the crystallization conditions of the amorphous silicon or if the laser energy is unstable relative thereto. Way. delete The method of claim 6, And when the changes in the reflected light are large and distinct, stripes are distributed over the surface of the crystallized silicon, which exhibits poor crystallization quality and the laser energy is inappropriate or unstable, simultaneously monitoring the formation of the laser crystallized silicon. delete delete A device for inspecting laser crystallized silicon applied to a low temperature poly Si (LTPS) process, An excimer laser annealing (ELA) machine that irradiates amorphous silicon on an insulating substrate with a laser beam in a line scanning manner to deform into crystallized silicon, A white light source for irradiating the surface of the crystallized silicon on the substrate, the white light source for irradiating the surface of the crystallized silicon at an angle of about 10 to 85 degrees with respect to a plane of the substrate, and Inspection of the laser crystallized silicon, comprising a camera which is irradiated by the light source to examine the crystallization state of the surface of the crystallized silicon and then captures reflected images of the surface of the crystallized silicon on the same side as the light source. Device. The method of claim 11, And a computer for receiving and analyzing the images captured by the camera to monitor the crystallization state of a selected area on the surface of the crystallized silicon and make immediate process adjustments. The method of claim 12, Inspection apparatus of laser crystallized silicon in which the uniformity, contrast and gray scale of the light intensity of the images in the selected area are analyzed to monitor the crystallization state of the selected area and to immediately adjust the laser energy of the laser beam. . The method of claim 11, And the camera captures the reflected images of the surface of the crystallized silicon on the entire substrate after being irradiated by the light source. delete delete The method of claim 11, And the white light source comprises green light. The method of claim 11, And the camera is oriented vertically within the irradiation angle range of the white light source. The method of claim 11, And the camera is oriented horizontally in a direction perpendicular to the direction of the line scanning of the laser beam. The method of claim 11, And the camera is oriented horizontally in a direction parallel to the direction of the line scanning of the laser beam.

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